MP6545

– 45V, 2.5A, SIMPLE THREE-PHASE POWER STAGE

MP6545 Rev. 1.1

MonolithicPower.com

13

5/12/2023

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OPERATION

The MP6545 is a three-phase power stage

designed to drive brushless DC (BLDC) motors

or other loads. It integrates six N-channel power

MOSFETs connected as three half H-bridges,

with a 2.5A current capability. The device

operates across a wide 4.5V to 45V supply

input voltage (VIN) range.

nSLEEP and nRESET

Pull the nSLEEP pin low to force the MP6545 to

enter a low-power sleep mode. In this mode,

the gate driver charge pump stops, and all the

internal circuits and outputs are disabled. All

inputs are ignored when nSLEEP is active low.

When the MP6545 exits sleep mode, 600µs

must pass before driving the motor. This allows

the internal circuitry to stabilize. nSLEEP has

an internal pull-down resistor.

Pull the nRESET pin low to reset the latched

protection

features,

including

over-current

protection (OCP) and over-voltage protection

(OVP), as well as to disable the outputs to a

high-impedance (Hi-Z) state.

Input Interface

The MP6545 includes three half-bridges that

operate independently. The device has high-

side (HS) and low-side (LS) inputs for each of

the output pins. Table 2 shows the HSx and

LSx input logic.

Table 2: HSx and LSx Input Logic

HSx

LSx

OUTx

0

0

Hi-Z

0

1

L

1

0

H

1

1

Hi-Z

Note that all logic inputs have weak, internal

pull-down resistors.

Automatic Synchronous Rectification

If the output high-side MOSFET (HS-FET) and

low-side MOSFET (LS-FET) are turned off, then

the recirculation current must continue to flow

when driving current through an inductive load.

This current is typically passed through the

MOSFET body diodes. To prevent excess

power dissipation in the body diodes, the

MP6545 implements automatic synchronous

rectification.

If both the HS-FET and LS-FET are turned off

and the voltage on an OUTx pin (VOUTx) is

pulled below ground, then the LS-FET turns on

until the current flowing through it approaches

0A, or until the HS-FET is commanded to turn

on. Similarly, if VOUTx exceeds VIN, then the HS-

FET turns on until the current approaches 0A,

or until the LS-FET turns on.

Internal Supplies (VREG and VCP)

The internal regulators generate a 5V supply

(VREG) for the LS gate drive, and a supply

exceeding VIN by 5V (VCP) for the HS gate drive.

These supplies require external capacitors.

The

VREG

pin

requires

a

1µF

ceramic

capacitor to ground. Meanwhile, the VCP pin

requires a 1µF ceramic capacitor to VIN. Both

capacitors should be X7R ceramic capacitors,

and rated for at least 16V.

Connect the charge pump flying capacitor

between the CPA and CPB pins using a 100nF

ceramic capacitor (X7R) rated for at least the

maximum VIN.

nFAULT

The MP6545 provides a nFAULT pin to report

to the system if a fault condition such as OCP,

OVP, or over-temperature protection (OTP)

occurs. nFAULT is an open-drain output and is

pulled low during fault conditions. If used,

nFAULT should be pulled high via an external

pull-up resistor.

Over-Current Protection (OCP)

OCP circuitry limits the current through the HS-

FET and LS-FET by disabling the gate driver. If

the over-current (OC) limit threshold is reached

and lasts for longer than the OC deglitch time

(tOCP), then all the MOSFETs in the H-bridge

are disabled and nFAULT is pulled low. The

driver remains disabled until the device is reset

by pulling nRESET low, or cycling the power on

the MP6545.

OC conditions on both the HS and LS devices

(i.e. an over-current condition to ground, supply,

or across a motor winding) all result in an OC

shutdown.